The present invention is related to a copending patent application, Ser. No. 315,403 entitled "Method and System for Controlling Combustion in Internal Combustion Engines," by Antoni K. Oppenheim, now U.S. Pat. No. 4,924,828, whose disclosure is incorporated herein by reference. This application describes in detail how improved control over combustion can be achieved by causing the process of combustion to take place within certain distinct fluid dynamic structures formed by jets. Such fluid dynamic structures are called plumes.
Their characteristic feature is a relatively high level of rotation in the form of a sequence of more or less convoluted vortex rings as well as swirl (i.e. azimuthal rotation around the axis of the jet), which are fluid motions that induce entrainment or inhalation of the surrounding charge into their midst. Under such circumstances the process of combustion takes place primarily inside the plumes rather than on their boundaries. When the velocity of rotation is slowed down by momentum exchange associated with entrainment and expansion due to the exothermicity of combustion, the inhaling effects subside and the plume enters the stage of puff, i.e. a cloud of gaseous products of combustion, by now in an arrested state of rotation, which becomes enveloped by a flame front. The key to a successful operation of the invention is to maximize the action of the plume and minimize that of the puff. Towards this end, the progress of combustion in the engine is controlled by a timed, sequential injection of a plurality of jets forming plumes, so that the head space of the cylinder is progressively filled by their evolving structures. The head space is eventually entirely filled by adjacent plumes as they burn by combustion taking place in their interior before reaching the stage of a puff, thus denying the flame-fronts the usual dominating role in the propagation of the combustion process. The above cited application further explains in detail the underlying reasons for the advantages of causing combustion to take place within multiple plume structures wherein the formation and propagation of flame fronts at their boundaries is inhibited. Since the latter is the major reason for the development of combustion instabilities as well as the formation of pollutants and, especially, particulates (soot), these harmful effects are thereby obviated.
The principle of controlling combustion by resorting to plumes within which reactants are mixed and caused to react, is generally applicable to any known system of reactants in an internal combustion engine. The copending patent application, Ser. No. 315,405 entitled "Pulsed Jet Combustion Generator for Premixed Charge Engines" by Antoni K. Oppenheim, Horton E. Stewart, and Kenneth Hom, now U.S. Pat. No. 4,926,818, addresses an important subset of reactants and reaction conditions, i.e., the combustion of fuels such as more volatile hydrocarbons and/or alcohol in air, carried out in the compressed premixed charge of the so-called Otto type engine. In accordance with the above cited invention, spark ignition systems and the attendant flame propagation mode of combustion are replaced by multiple generators of jets of combustion products that form plumes which entrain the surrounding premixed reactants and upon ignition by contact with the products, burn them in their interior.
The present invention addresses another important subset of reactants and reaction conditions, i.e. diesel engines, in which liquid fuel is introduced into air which has been heated to such a degree so as to initiate combustion of the fuel. In conventional diesel engines the fuel is normally a higher chain length hydrocarbon of a lower volatility injected in liquid form into air heated by piston compression at a volumetric ratio of typically twenty to one. The present invention essentially replaces the conventional diesel injector mechanism by a plurality of plume forming jet generators. The plumes contain fuel in the form of very fine droplets within a carrier air jet streams, forming, upon injection into the compressed air, plumes that consist of a sequence of large scale, whirlpool type, eddy structures associated with rotation to entrain (inhale) the surrounding medium into their midst. In this case it is the hot piston compressed air which is entrained into the interior of the plume, causing it to get in contact and consequently react with the fuel carried in the interior of the plume by the colder airstream. It is important to note that by causing combustion to take place within the reacting plumes, whose magnitude and timing is determined by external action, it is possible to control combustion by adjusting external parameters so that it takes place under locally premixed conditions and thus subdue significantly the tendency to form particulates (soot) and develop combustion instabilities such as knock.
In practice, each cylinder would be outfitted with a plurality of such plume generators, permitting control over the combustion process by adjusting the quantities and sequential timing of the reactants introduced thereby into the head space. The mature size of each plume upon completion of its function of carrying out the combustion of the fuel occupies between about 1/2 to 1/8 the volume of the head space at top dead center. Each plume generator may also include means for introducing into said fuel metered quantities of fuel additives, which may be compounds for either accelerating or decelerating combination reactions.